The present invention is directed to golf ball compositions and, in particular, polymer compositions including highly-neutralized polymers and blends thereof.
Conventional golf balls can be divided into two general classes: solid and wound. Solid golf balls include one-piece, two-piece (i.e., solid core and a cover), and multi-layer (i.e., solid core of one or more layers and/or a cover of one or more layers) golf balls. Wound golf balls typically include a solid, hollow, or fluid-filled center, surrounded by a tensioned elastomeric material, and a cover. It is also possible to surround a hollow or fluid-filled center with a plurality of solid layers. Solid balls have traditionally been considered longer and more durable than wound balls, but many solid constructions lack the xe2x80x9cfeelxe2x80x9d provided by the wound construction.
More recently, by altering ball construction and composition, manufacturers have been able to vary a wide range of playing characteristics, such as compression, velocity, xe2x80x9cfeel,xe2x80x9d and spin, optimizing each or all be optimized for various playing abilities. In particular, a variety of core and cover layer(s) constructions, such as multi-layer balls having dual cover layers and/or dual core layers, have been investigated and now allow many non-wound balls to exhibit characteristics previously maintainable in a solid-construction golf ball. These golf ball layers are typically constructed with a number of polymeric compositions and blends, including polybutadiene rubber, polyurethanes, polyamides, and ethylene-based ionomers.
Ionomers, and in particular ethylene xcex1,xcex2-ethylenically unsaturated carboxylic acid copolymers or a melt processible ionomer thereof, are a preferred polymer for many golf ball layers. One problem encountered with the use of ionomers as stiff layers, however, is the unprocessability of the material as the percent of neutralization of the acid group increases. Ionomers are stiffened by increasing the amount of neutralization by a metal cation or a salt thereof. Once the percent of neutralization is greater than about 60% (depending on metal cation selected), the melt flow of the ionomer becomes too low and the ease of processablilty decreases or disappears altogether. For tri-valent cations, the percent neutralization at which the polymer becomes unprocessable can be significantly lower.
There is a need, therefore, for ionomer compositions that are neutralized at high percentages, but in a manner that still allows resultant polymer compositions to be processible. The present invention describes such compositions and there use in a variety of golf ball core and cover layers.
The present invention is directed to a golf ball comprising a core comprised of a polymer containing an acid group neutralized by an organic acid or a salt thereof, the organic acid or salt thereof being present in an amount sufficient to neutralize the polymer by at least about 80%, wherein the core has a first Shore D hardness, a compression of no greater than about 80, and a diameter of no less than about 1.53 inches; and a cover comprised of a material having a second Shore D hardness at least 10 points less than the first hardness.
Additionally, the present invention is also directed to a golf ball comprising a core comprised of a polymer containing an acid group neutralized by an organic acid or a salt thereof, the organic acid or salt thereof being present in an amount sufficient to neutralize the polymer by at least about 80%, wherein the core has a first Shore D hardness, a compression of no greater than about 80, and a diameter of no less than about 1.53 inches; and a cover comprised of a material having a second Shore D hardness at least 10 points greater than the first hardness.
In one embodiment of the above, the polymer comprises ionomeric copolymers and terpolymers, ionomer precursors, thermoplastics, thermoplastic elastomers, polybutadiene rubber, balata, grafted metallocene-catalyzed polymers, non-grafted metallocene-catalyzed polymers, single-site polymers, high-crystalline acid polymers, cationic ionomers, and mixtures thereof.
In another embodiment of the above, the organic acid is selected from the group consisting of aliphatic organic acids, aromatic organic acids, saturated mono-functional organic acids, unsaturated mono-functional organic acids, and multi-unsaturated mono-functional organic acids. Preferably, the salt of organic acids comprise the salts of barium, lithium, sodium, zinc, bismuth, chromium, cobalt, copper, potassium, strontium, titanium, tungsten, magnesium, cesium, iron, nickel, silver, aluminum, tin, calcium, stearic, bebenic, erucic, oleic, linoelic, dimerized derivatives, and mixtures thereof.
In another embodiment of the above, the core further comprises a second polymer component in an amount sufficient to reduce the core compression to less than or equal to about 70. Further, preferably the second polymer component has a Shore D hardness of about 40 or greater. It is also preferred that the second polymer component comprises ionomeric copolymers and terpolymers, ionomer precursors, thermoplastics, thermoplastic elastomers, polybutadiene rubber, balata, grafted metallocene-catalyzed polymers, non-grafted metallocene-catalyzed polymers, single-site polymers, high-crystalline acid polymers, cationic ionomers, and mixtures thereof.
In one embodiment of the above, the organic acid or salt thereof is present in an amount sufficient to neutralize the polymer by at least about 90%. In a preferred embodiment, the organic acid or salt thereof is present in an amount sufficient to neutralize the polymer by at least about 100%. Further, at least one of the polymer or second polymer component is partially neutralized by a metal cation.
In another embodiment, the core has a diameter of about 1.58 inches or greater. The cover may be comprised of a castable reactive liquid material or the cover is cast or reaction injection molded over the core. Preferably, the cover is comprised of a polyurethane.
The present invention is also directed to a golf ball comprising a core comprising a center and an outer layer, the center being comprised of a thermoset rubber and the outer layer being comprised of polymer neutralized with an organic acid or a salt thereof, the organic acid or salt thereof being present in an amount greater than about 10 weight percent such that the polymer is fully neutralized, wherein the outer layer has a first Shore D hardness and the core has a compression of less than or equal to about 90 and a diameter of about 1.53 inches or greater; and a cover being comprised of a castable reactive liquid material having a second Shore D hardness being at least 10 points less than the first hardness.
In one embodiment, the outer layer further comprises a softening copolymer in sufficient weight percentage to reduce the core compression to less than or equal to about 70. In another embodiment, the core has a diameter of about 1.58 inches or greater. Preferably, the cover is comprised of a castable reactive liquid material. The cover may also be cast or reaction injection molded over the core. It is preferred that the cover is comprised of a cast polyurethane. In another embodiment, the golf ball further comprises an intermediate layer being comprised of an ionomer having a Shore D hardness that is at least 10 greater than the first Shore D hardness.
In an alternative embodiment, the core is surface treated by plasma treatment, corona discharge, chemical treatment or mechanically treated.
The present invention is also directed to a golf ball comprising a core comprised of a thermoset rubber having a diameter of about 0.5 to 1.55 inches; a cover disposed over the core having a shore D hardness of about 55 or less; and an intermediate layer being comprised of a polymer neutralized by an organic acid or a salt thereof, the an organic acid or a salt thereof being present in an amount sufficient to neutralize the polymer by at least about 100%.
Preferably, the cover is comprised or a polyurethane. In one embodiment, the intermediate layer has a Shore D hardness of at least about 62. In another embodiment, the cover has a thickness of about 0.04 or less. In still another embodiment, the core has a compression of about 70 or less and a diameter of at least 1.4 inches.
The present invention is also directed to a golf ball comprising a center comprised of a liquid, the center having a diameter of about 1.0 inches or less; an intermediate layer being comprised of a polymer neutralized with an organic acid or a salt thereof, the an organic acid or a salt thereof being present in an amount greater than about 10 weight percent such that the polymer is saturated, the intermediate layer being disposed about the center to form a core; and a cover disposed over the core.
Preferably, the cover is comprised of a polyurethane. Additionally, the core is further comprised of an outer layer comprised of a thermoset rubber disposed between the intermediate layer and the cover. In another embodiment, the outer layer has a hardness that is at least 5 points less than a hardness of the intermediate layer.